1. Field of the Invention
The present invention relates to coupling of plastic pipes and, more particularly to coupling of plastic pipes by fusion welding or through a mechanical seal.
2. Description of the Prior Art
Prior to the advent of plastic pipe, most piping was made out of metal, such as copper, stainless steel or iron. The particular metal used for the piping was dependent upon the application. For example, water could be transported through copper and/or cast iron pipes. However, acids had to be transported in stainless steel pipe. Some of the metal pipe, such as copper and stainless steel, was expensive to manufacture and install. Typically, the pipe was either brazed or welded together. In some instances, mechanical type joints were provided for pipe connections. In today""s market, all of these arrangements are expensive to manufacture and install.
Plastic pipe overcomes many of the expenses associated with metal pipe. Plastic pipe is inexpensive to manufacture and relatively easy and inexpensive to connect together. In the case of thermoplastic materials, such as polypropylene, the pipe can be welded together by providing a polypropylene sleeve with electrical heating elements embedded therein. This process is known as fusion welding. Fusion welded pipe is particularly applicable in situations where acid passes through the plastic pipe. Polypropylene pipe can be secured to each other through mechanical seals. In some applications, mechanical seals are preferable to the fusion welding.
In the past, different pipe couplings were provided for fusion sealing and mechanical sealing. This resulted in an increase in inventory required by the installer, such as the mechanical contractor or plumber, since two separate types of couplings were required, one for mechanical sealing and the other for fusion welding.
Therefore, it is an object of the present invention to provide a single coupling for use with mechanical sealing and fusion welding of plastic pipe.
The present invention is a piping system that includes a first pipe, a second pipe, a coupling, an arrangement for securing the first pipe to the coupling and an arrangement for securing the second pipe to the coupling. The first pipe is made of thermoplastic material having a first pipe first end. The second pipe is made of thermoplastic material having a second pipe first end. The coupling includes a body having a coupling first end and a coupling second end. The body has an outer surface and an inner surface. The inner surface defines a passageway and a lip positioned between the coupling first end and the coupling second end. The first pipe first end is received by the coupling first end and the second pipe first end is received by the coupling second end. The first pipe first end and the second pipe first end are positioned on opposite sides of the lip.
The pipe coupling can include pipe coupling threads defined on the outer surface of the coupling configured to engage with a nut, a first tapered inner surface adjacent the coupling first end and a second inner tapered surface adjacent the coupling second end and a plurality of circumferential rings defined on the inner surface. Axial ribs can be defined on the coupling outer surface and positioned between the threads positioned adjacent the coupling first end and the coupling second end.
The arrangement for securing the first pipe to the coupling and the arrangement for securing the second pipe to the coupling can be accomplished through a fusion seal or a mechanical seal. The fusion seal includes a sleeve made of thermoplastic material having an electrically resistive wire embedded therein and two leads attached to the electrically resistive wire extending from the sleeve. The sleeve is configured to be sandwiched between the pipe coupling and a thermoplastic pipe with the two leads extending from the piping coupling. The mechanical seal includes a flexible body received between the pipe coupling and the first pipe and a nut, the flexible body is held in place by the nut coacting with the pipe coupling and an end of the flexible body. The nut includes inner threads that coact with the pipe coupling threads. The nut includes an annular lip that defines a passageway configured to permit a thermoplastic pipe to pass there through, the annular lip contacts an end of the flexible body of the mechanical seal and holds the flexible body of the mechanical seal in place. The flexible body also includes a tapered portion adapted to coact with the first tapered inner surface of the pipe coupling.
The present invention can be provided as a kit for joining thermoplastic pipe together.
Further, the present invention is a method for joining two thermoplastic pieces of pipe, that includes the steps of:
a) providing two pieces of thermoplastic pipe;
b) attaching either a fusable seal or a mechanical seal at the ends of each the pieces of thermoplastic pipe;
c) passing the ends of the pieces of thermoplastic pipe with the seals through ends of a thermoplastic pipe coupling and sandwiching the seals between the pipe coupling and the pieces of thermoplastic pipe; and
d) forming a fluid tight seal between the pieces of thermoplastic pipe and the pipe coupling by either compressing the mechanical seal with a nut coacting with the pipe coupling or heating the sleeve until the sleeve and adjacent portions of the pipe coupling and the pipe melt.